A blaze in a rural part of Pike County, Ky., killed four young children, ages 5, 4, 2, and 6 months, and their father, fire officials said. The children’s mother was injured in the fire and rushed to the hospital. The blaze broke out around 2:30 a.m. in a home three hours southeast of Lexington in the eastern coal field area of the state, officials said.

The cause of the fire had not been determined by Wednesday morning.

In a separate fire in Conyers, Ga., four children, including an infant, died Tuesday night when a fire broke out in a duplex in the Atlanta suburb, authorities said.

Police officers arrived at the home within "30 seconds to a minute" of receiving a 911 call, Police Maj. Mike Waters told NBC News early Wednesday. However, the children -- who ranged in age from 8 months to 7 years -- could not be rescued.

"When the officers arrived, the duplex was fully involved in fire," Waters said. "They were told there might be children upstairs trapped in the fire. When they tried to rush up the stairs with their fire extinguishers, they were met with flames.

David Goldman / AP

An Alcohol, Tobacco and Firearms agent inspects the second floor scene of a house fire that killed four children, including an infant, Wednesday, Jan. 9, 2013, in Conyers, Ga.

"They were not able to get up the steps. It was an intense fire on the second floor of the home."

A 6-year-old child survived with no serious injuries, Waters said, adding that the child told police that his mother had thrown him from a second-floor window. The mother was severely burned and was taken to an Atlanta hospital, and the children's grandmother made it out of the home without injury, Waters said.

The children who died included three girls and a boy. All were on the second floor, which had two bedrooms and a bathroom, Waters said. The other half of the duplex was empty.

The cause of the fire remained unclear Wednesday morning, and investigators were preparing to comb through the house for clues.

"Naturally, after an incident like this the fire department would conduct a full investigation," Waters said.